1. Field of the invention
The present invention relates to a high temperature corrosion-resistant and abrasion-resistant coated member suitable for use under a high temperature corrosive and abrasive environment, such as a turbine rotor blade and a stator blade of a gas turbine for power generation, and a manufacturing method thereof.
2. Description of the related art
Recently, in a gas turbine, there has been a tendency to use poorly graded fuels for reducing the running cost. A turbine which uses a fuel made from coals gasified in a pressurized fluid bed boiler among the poorly graded fuels is under a more severe high temperature corrosive environment because of corrosive components such as Na (sodium), K (potassium), Cl (chlorine) or S (sulfur) than a turbine which uses conventional natural gas fuel or oil fuel, and at the same time, it is under a very severe abrasive environment because of flying particles (fine grain flying ashes). Therefore, in high temperature parts of a gas turbine which use a fuel made from coals gasified in a pressurized fluid bed boiler, especially in a turbine rotor blade or a stator blade whose service conditions are severe, for example, the materials shown below are used. That is, they are a material in which as shown in FIG. 6, an Al diffusion and infiltration coating is given on the surface of a base material 1 such as a Co radical alloy or an Ni radical alloy to form an Al diffusion layer 4 for improving the corrosion resistance, and a material in which as shown in FIG. 7, an MCrAlY (M is Co, Ni, Co+Ni, or Fe) thermal spraying coating is given on the surface of a base material 1 to form an MCrAlY layer 5. However, these Al diffusion layer 4 and MCrAlY layer 5 are essentially formed for the principal purpose of improving the corrosion resistance, and the purpose of reducing the abrasion because of flying particles (erosion) is a minor one.
Furthermore, as shown in FIG. 8, a thermal spray coating of chromium carbide [75 wt % Cr3C2xe2x80x9425 wt % (50 wt % Nixe2x80x9450 wt % Cr)] is given onto the surface of a base material 1 to form a chromium carbide layer 6, and such material is often used for a steam generating tube of a boiler or the like used under an abrasive environment. This material is excellent in abrasion resistance because of the fine scattered Cr3C2, but it is not used for a turbine blade which is a rotary member from the view point of the inferiority in ductility and tenacity because of a low matrix (connecting material) content. Furthermore, the Nixe2x80x94Cr alloy of the above matrix is not used for a turbine blade also because the alloy is inferior to the MCrAlY coating in terms of high temperature corrosion resistance and oxidation resistance. Therefore, previously, there has been a problem that the lifetime of a turbine blade is extremely short in a rotor blade and a stator blade of a gas turbine used under an environment like this. By the way, the temperature at this damaged parts is about 600 to 800xc2x0 C.
That is, in the conventional technology, no corrosion-resistant and abrasion-resistant coated member has been known which has both the corrosion and oxidation resistance and the abrasion resistance at the same time and which is capable of being used for parts exposed to the severe corrosive environment and the severe abrasive environment, for example, like a turbine rotor blade or a stator blade of a fluid bed boiler combustion gas turbine. Either the corrosion and oxidation resistance or the abrasion resistance has been severely compromised, and the lifetime of a member such as a turbine blade has been short.
In view of this state of art, it is an object of the present invention to provide a high temperature corrosion-resistant and abrasion-resistant coating member suitable for a member used under a severe high temperature corrosive environment and a very severe abrasive environment because of flying particles, like a high temperature part of a gas turbine using poorly graded fuels, and a manufacturing method thereof.
The present invention has the following 4 embodiments:
(1) A manufacturing method of a high temperature corrosion-resistant and abrasion-resistant coated member, which comprises the step of performing an Al diffusion and infiltration treatment after giving a chromium carbide coating on the surface of a base material.
(2) A high temperature corrosion-resistant and abrasion-resistant coated member comprising a chromium carbide coating layer whose outside surface is an Al diffusion layer and which is formed on the surface of a base material.
(3) The high temperature corrosion-resistant and abrasion-resistant coated member according to the above (2), wherein the thickness of the chromium carbide coating layer including the Al diffusion layer is 50 to 500 xcexcm, and the thickness of the Al diffusion layer is 5 to 100 xcexcm.
(4) A gas turbine blade comprising a chromium carbide coating layer whose outside surface is an Al diffusion layer and which is formed on the surface.
The high temperature corrosion-resistant and abrasion-resistant coated member according to the present invention is a member in which the corrosion resistance and the oxidation resistance are improved by diffusing and infiltrating Al into the surface of a chromium carbide coating layer with an excellent high temperature abrasion resistance, and it has both good corrosion and oxidation resistance and good abrasion resistance at the same time.
Accordingly, by applying the high temperature corrosion-resistant and abrasion-resistant coating member according to the present invention to a gas turbine or the like, it is possible to provide a high temperature part such as a turbine rotor blade and a stator blade, or a burner which can withstand a long time service under a very severe environment where abrasion and corrosion occurs at the same time, for example, in a pressurized fluid bed combustion gas turbine.
Furthermore, according to the method of the present invention, it is possible to easily manufacture a high temperature corrosion-resistant and abrasion-resistant coated member having the above performance.